In the printing industry, printing lines with a plurality of workstations are used, with which sheet-like material can be processed. Processing steps include for example printing, coating, coupling, creasing, perforating and/or folding. A printing line with a plurality of workstations is disclosed for example in [1], JP4327996. Typically, printing lines of this kind are adapted to precisely defined processes that subsequently cannot be altered without changing the structure of the printing line. Often, all sheets are transported and processed by the printing line in the same manner. Devices installed in such a printing line are adapted to a specific task or function required at a given point within the printing line.
A printing line can also be integrated into a unitary processing unit such as the sheet stacking apparatus and image forming apparatus disclosed in [2], US2008157466A1. The modules of this apparatus are adapted to individual tasks and are firmly integrated in the apparatus.
From [3], US2007120934A1, a mixed output printing system is known that comprises a first and a second printing unit that deliver paper sheets to a merging module, that comprises a sheet rotor which can turn the sheets by 90°. Further, an input buffer, from which sheets can be taken, and an output buffer, on which sheets can be stacked, are provided. This system allows transferring sheets from a first printing line to a second printing line aligned perpendicularly thereto. The merging module comprises controllable deflectors and at least one merging path, along which the sheets can be merged, and at least one path, along which sheets can be transported directly from a first workstation to a second workstation. For obtaining several transport paths within the system a plurality of roller pairs is provided, which guide the sheets along the selected paths. Hence, conveying devices of this kind exhibit a high mechanical complexity and, in spite of additional functions such as a by-pass function, a relatively small flexibility.
Besides the complex mechanical system and the costs related thereto, large rooms are required for this conveyor technology.
[4], U.S. Pat. No. 5,979,890A, discloses a sheet transfer system that uses a conveyor belt which attracts the back side of the sheet under vacuum along a conveyance passage including a bent portion. With the conveyor belt, sheets can selectively be transported to a first or to a second sheet sorter. A first conveyor belt is used to transport sheets vertically down at a related sorter. A second conveyor belt is used for transporting a sheet past the first sorter to the second sorter. Along this transport path the sheets are transported on top of the second conveyor belt, which is arranged between the sheets and the first sorter that is by-passed. Hence, this system requires various conveyor belts for transporting sheets to different destinations.
Further, also in this system sheets are transported from first to second processing units that are adapted to a specific function.
Further for directing the sheets to the related destinations various air blowers are provided that can direct an air flow against the upper surface of the conveyor belt at a bent portion of a conveyance passage so that the sheet can be bent along the surface of the conveyor belt and can either be transported along the first conveyor belt down the first sorter or along the second conveyor belt past the first sorter. The system therefore requires space for the rather voluminous air blowers which allow forcing a sheet into a desired direction. Further, the air flows generated by various air blowers within a device may cause interferences and related disturbances. Further, such air blowers which act from a distance require considerable energy, when generating the required air flows.
Modules for transporting sheets with conveyor belts that allow the application of air suction are known from [5], DE102007024916A1.
The present invention is therefore based on the object of providing an improved device and an improved method for conveying sheet-like material. Further, an improved conveyor system with at least one processing line shall be created.
In particular a device for conveying sheet-like material shall be defined, which allows creating two or more transport paths and conveying functions in a simple manner and with reduced volume so that it can be installed in small rooms.
The inventive conveyor device shall allow implementing two or more process functions, such as functions for picking up, delivering, merging, sorting, deflecting and distributing sheets in a simple and efficient manner.
The transported sheets shall be treated smoothly so that damages are avoided. Further the transported sheets shall be sensed optically in order to optimally control the conveying process.
It shall be possible to create conveying systems with at least one printing line or with a plurality of printing lines that cross one another with reduced efforts and reduced space requirements.
It shall be possible to use inventive conveying devices advantageously in one or more positions within a printing line, in order to locally implement one or more of the above-mentioned process functions. Thereby, an adaptation to different process functions shall be implementable by a simple change of the operation mode with the installed software. Hence, with inventive conveyor devices, it shall be possible to construct and change printing lines with reduced effort.